Infectious Laryngotracheitis (ILT) is an acute highly contagious respiratory disease of chickens. It has significant economic importance due to mortalities and the drop in egg production. In this study, seventy samples from different layer farms were collected from the outbreaks that occurred in Kalubia province, Egypt, at the period from February 2018 till May 2019 to detect ILTV by molecular characterization through polymerase chain reaction assay (PCR) as well as isolation on the specific pathogen free- embryonated chicken eggs (SPF-ECEs) through chorioallantoic membrane (CAM) route. Post mortem examination of infected chickens revealed hemorrhagic tracheitis with fibrino-hemorrhagic casts and caseated materials. The PCR revealed amplification of a 688bp fragment of Infected Cell Protein 4 (ICP4) gene. Following that, seven samples were sequenced and phylogenetically analyzed. Sequence analysis of the ICP4 gene of these samples revealed complete identity with TCO (tissue culture origin) vaccines and the vaccine-related strains, which were previously isolated from Giza, Sharkia, Kafrelsheikh, and Fayoum provinces through the years 2007 to 2018. Inoculation of ILTV PCR positive samples on SPF-ECE appeared as yellowish-white pock lesions on the inoculated CAM from the first passage. From these results, we can say that ILTV circulating in Egypt is a vaccinal strain that regains its virulence from the back passage in birds and causes outbreaks all over the country. |
